Foam generating system with a substantially constant foam delivery rate

ABSTRACT

A foam generating system utilizes a positive displacement pump to deliver liquid at a substantially constant liquid delivery rate to a foam generator. The liquid delivery rate is independent the pressure of air supplied by a pressurized air source to the foam generator, the back pressure of the foam generator itself, the volume of liquid in a supply tank, and the pressure drop of the connection line from the foam generator to a user appliance. The foam generator delivers foam at a constant foam delivery rate (expressed as weight of foam per unit time) to the user appliance. The liquid supply tank is vented to atmosphere.

BACKGROUND OF THE INVENTION

[0001] Field of the Invention The invention relates to a foam generating system, and in particular, to a foam generating system that delivers foam to a user appliance at a substantially constant foam delivery rate (expressed as weight of foam per unit time).

[0002] Description of the Prior Art Systems for generating foam by combining pressurized air with a liquid (such as a liquid detergent) are well known. Such systems utilize various porous media to shear the supplied liquid and air to generate foam.

[0003] U.S. Pat. No. 4,366,081 (Hull) discloses a foam generating system having a mixing column containing a dual bed of steel wool-like material. A stream of pressurized water aspirates a liquid from a vented reservoir and conveys the same to the base of the column. Compressed air is supplied to the column through a separate pressurized line. The flow rates of both the air and the liquid are controlled by separate valves.

[0004] U.S. Pat. Nos. 4,901,925 and 5,238,155 (both to Blake) disclose a single air supply that pressurizes a reservoir containing the liquid and forces the same toward the mixing chamber containing the porous media. In such a foam generating system care must be exercised to insure that the structural integrity of the liquid supply reservoir is sufficient to withstand the forces imposed by the pressurized air supply.

[0005] Commercial carpet cleaning apparatus typically involves the application of a liquid detergent to the carpet surface followed by a rubbing, scrubbing or brushing action imposed by a carpet cleaning assembly. In an extraction cleaning system the liquid and entrained or dissolved dirt are subsequently removed from the carpet by vacuum suction. In an encapsulation cleaning system the liquid cleaning agent is not immediately removed, but acts to encapsulate the dirt for subsequent removal by dry vacuum. In either case time is allotted to allow the carpet to “air dry” after the cleaning cycle before it is exposed to further traffic.

[0006] Sufficient cleaning liquid must be applied to the carpet surface to properly dissolve and carry away dirt and soil. Complete dispersion of the cleaning liquid into and throughout the carpet tufts is required in order to clean the carpet thoroughly.

[0007] While there must be sufficient cleaning liquid applied to clean the flooring material in question an excess of liquid is also undesirable. The application of excessive liquid makes it difficult for carpets to dry in a timely manner. This can be especially important where carpets must be cleaned and returned to service promptly, as in the hospitality industry.

[0008] Another negative aspect of excessive liquid is that cleaning liquid may leave residual material on carpet fibers which will attract dirt and cause the carpet to appear matted and dirty soon after cleaning. While special cleaning formulations can somewhat mitigate this problem, such formulations are expensive, hence application of excessive amounts of liquid is costly.

[0009] Owing to these deficiencies with liquid cleaning agents foam detergent has been found especially useful for carpet cleaning. Foam application has been shown to provide good dispersion of the chemical cleaning agent into rugs and carpets, enabling effective cleaning with less liquid. Unfortunately, foam-based cleaning apparatus of the prior art is somewhat unstable, in the sense that excessively heavy foam may be delivered at times, leading to higher material cost, longer drying times, and streaking. At other times lighter foam is delivered resulting in insufficient cleaning.

[0010] U.S. Pat. No. 6,276,613 (Kramer) discloses a foaming system for a floor cleaning apparatus that utilizes a dual column foam generator and a single air supply that both pressurizes a liquid supply tank and supplies air to the foam generator. The dual columns of the foam generator are believed to be positionally sensitive, meaning that unless the columns are substantially aligned at the same elevation, gravity will affect the flow through one of the columns. In addition, the use of a pressurized tank system requires that the tank be structurally robust to prevent rupture. Limitations on tank pressure to conform to the structural capability of the tank may also limit the distance over which liquid may be efficiently supplied to the dual foam generating columns.

[0011] In view of the foregoing it is believed advantageous to provide a foam generating system that has a substantially constant foam delivery rate (expressed as weight of foam per unit time) regardless of the operating pressures at various points in the foam generating system. It is believed to be of further advantage to provide a foam generating system which does not utilize a dual column foam generator and which does not require pressurization of the liquid supply tank. Such a foam generating system is believed especially practical for use in connection with a carpet cleaning apparatus.

SUMMARY OF THE INVENTION

[0012] The present invention is directed to a foam generating system including a foam generator having an inlet port and an outlet port, a source for supplying pressurized air at a predetermined air pressure to the inlet port of the foam generator, and a supply tank for carrying a liquid. The outlet port of the foam generator is connectible to a user appliance through a connection line having a predetermined pressure drop. The introduction of pressurized air and a liquid at the inlet port of the foam generator results in the delivery of foam at the outlet port thereof. During operation the foam generator has a predetermined back pressure associated therewith. The foam generating system in accordance with the present invention is believed especially useful in a carpet cleaning apparatus with a carpet cleaning assembly as the user appliance connected to the outlet port of the foam generator.

[0013] The foam generating system of the present invention is improved in that it includes a positive displacement pump operable at a constant liquid delivery rate for pumping liquid, such as a liquid cleaning agent, from the supply tank to the inlet port of the foam generator. The liquid delivery rate from the pump to the inlet port of the foam generator is independent of the pressure of the air supplied by the pressurized air source, the back pressure of the foam generator, the pressure drop of the connection line, and the volume of liquid in the supply tank.

[0014] The supply tank is vented to atmosphere, avoiding the necessity of pressurizing the tank.

[0015] With the foam generating system of the present invention the delivery rate of foam from the outlet port of the foam generator for delivery to the user appliance (expressed as weight of foam per unit time) is substantially constant.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention will be more fully understood from the following detailed description, taken in connection with the accompanying drawings which form a part of this application, and in which:

[0017]FIG. 1 is a schematic diagram of a foam generating system of the present invention;

[0018]FIGS. 2A and 2B are respective side and front elevational views of the physical arrangement of the components of a foam generating system in accordance with the present invention in a “stand alone” configuration; and

[0019]FIGS. 3A through 3C are respective side elevational, rear elevational and plan views of a carpet cleaning apparatus incorporating a foam generating system in accordance with the present invention, while FIGS. 3D and 3E are side and front elevational views taken along the respective view lines in FIGS. 3C and 3A showing the physical arrangement of the components of a foam generating system in accordance with the present invention when used in a carpet cleaning apparatus.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Throughout the following detailed description similar reference numerals refer to similar elements in all Figures of the drawings.

[0021] With reference to FIG. 1 shown is a schematic diagram of a foam generating system generally indicated by the reference character 10 in accordance with the present invention. The functional elements comprising the foam generating system 10 are illustrated as lying within the boundaries of the dot-dash line in the schematic rendition of FIG. 1. As is discussed herein the form generating system 10 may be physically configured for “stand-alone” use as a source of foam to any user appliance (FIGS. 2A and 2B) or integrated within a carpet cleaning apparatus (FIGS. 3A through 3E). It should also be appreciated, however, that the foam generating system in accordance with the present invention may also be used in the environment of a fixed installation, such as the deposition of a foam agent (such as dye or other chemical agent) in a carpet manufacturing facility.

[0022] Functionally, the foam generating system 10 includes a foam generator 14 in the form of a column 14C having an inlet port 14I and an outlet port 14P. The outlet port 14P is provided with a suitable connection fitting 16. A connection line L associated with a user appliance A may be detachably connected (via the fitting 16) to the output port 14P of the foam generator foam generator 14. The introduction of pressurized air and a liquid at the inlet port 14I of the foam generator 14 results in the delivery of foam at the outlet port 14P thereof. During operation the foam generator 14 has a predetermined back pressure associated therewith. In use, the connection line L between the foam generator 14 and the user appliance A also has a predetermined pressure drop associated therewith.

[0023] Any well-known form of foam generating apparatus 14 may be used in connection with the present invention, although a foam generating column 14C in which glass beads 14B (FIGS. 2A, 2B and FIGS. 3D, 3E) are used as the shearing medium is preferred. The glass bead column is inherently stable, requires no external devices or auxiliary action for foam generation, and provides uniform high quality foam. Changes in the diameter of the glass beads, the length of the column, the diameter of the column are not significant contributors to the resultant performance of the system.

[0024] In practice, the foam generating column 14C may be fabricated from commercially available hardware elements assembled to provide a container for the glass beads and the inlet for air and liquid. For example, as seen in FIGS. 2B and 3E, a cylinder may be formed from a length of tubing 14T that is clamped (as by hose clamps 14H) at each end to a pair of threadedly engaged fittings collectively shown at 14F. Each of the outer fittings holds a screen retainer 14R for the glass beads 14B. The glass beads 14B must be installed so that when the fittings 14F are secured to the cylinder 14T the beads 14B are tightly packed. This precludes movement, channeling, and bypass of the flow that would defeat the shear action and foam generation.

[0025] The foam generating system 10 includes a source 18 for supplying pressurized air at a predetermined air pressure to the inlet port 14I of the foam generator 14. The pressurized air source 18 may take the form of an air compressor 18C such as that manufactured by Thomas Pump and Compressor, Sheboygan, Wis., and sold as model 639CE44. A filter 20 at the inlet of the pressurized air source 18 protects the system 10 from outside airborne contamination. The outlet of the pressurized air source 18 is connected to the inlet port 14I of the foam generator 14 through a line 18L.

[0026] A flow control device 22, such as a fixed orifice available from Spraying Systems Company, Wheaton, Ill., as model CP 4916-054, is disposed in the line 18L. The flow control device 22 establishes the ratio of air to liquid supplied to the inlet port 14I of the foam generator 14 and thus determines the “blow ratio”, or wetness, of the foam. An adjustable orifice may be used if a further level of user control is desired.

[0027] Liquid is supplied to the inlet port 14I of the foam generator 14 by a positive displacement pump 24 through a line 24L. The pump 24 draws liquid from a supply tank 28 that is connected to the inlet side of the pump 24 by a supply line 28L. Suitable for use as the pump 24 is the positive displacement pump manufactured by Autoclude Pumps, Ltd., Essex, England, and sold as model M1500-4S-2225. A positive displacement pump is preferred because once the supply lines to the generator 14 are charged, the foam generator 14 operates essentially an “instant on” and “instant off” manner that is especially useful in portable equipment. Also, changing flow rate is accomplished by simply changing the pump speed.

[0028] In accordance with the present invention the supply tank 28 has a vent opening 28V whereby the interior of the tank is vented to atmosphere. By venting the tank 28 to atmosphere, the sometimes significant time delay required for a pressurized tank system to reach its operative pressurization level is avoided. In addition, a vented tank avoids the necessity for relieving tank pressure before flow ceases.

[0029] Although forming part of the foam generating system 10, in some instances it may be desired to physically separate the tank 28 from the remainder of the functional elements forming the system 10. To this end the supply line 28L is provided with a suitable fitting 30 (similar to the fitting 16) whereby the tank 28 may be connected and disconnected from the pump 24. Since the tank 28 communicates with the suction side of the pump 24 the only limitation upon the distance at which the tank may be placed from the remainder of the system 10 is the “lift” or suction capability of the pump 24.

[0030] The system 10 is protected from liquid-borne contamination by a filter 34. The filter 34 may be conveniently disposed in either the line 24L (e.g., FIG. 2B) or the line 28L (e.g., FIG. 3D), as desired. The tank 28 may be drained by pumping liquid through a drain line 36L closed by a drain valve 36V.

[0031] In operation, owing to its positive displacement action whereby a fixed amount of liquid is transferred through the pump on each operational cycle, the pump 24 is operable to deliver liquid to the inlet port 14I of the foam generator 14 at a constant liquid delivery rate. The liquid delivery rate from the pump to the inlet port 14I of the foam generator 14 is independent of the pressure of the air supplied by the pressurized air source 18, the back pressure across the foam generator 14, the volume of liquid in the supply tank 28, and the pressure drop of the connection line L to the user appliance A. As a result, the delivery rate of foam from the outlet port 14P of the foam generator 14 to the user appliance A (expressed as weight of foam per unit time) is substantially constant.

[0032] As used throughout this application (including the claims) the term “substantially constant” in connection with either the liquid delivery rate to the foam generator or the foam delivery rate from the foam generator means that the weight of liquid or foam (in pounds or kilograms) per unit time does not vary substantially.

[0033] As noted, the system 10 of the present invention can be implemented in a mobile, cart-like “stand-alone” configuration. A typical implementation and the physical arrangement of the components of the foam generating system 10 in accordance with the present invention in a “stand alone” configuration is illustrated in FIGS. 2A and 2B.

[0034] In a “stand alone” configuration the supply tank 28 is mounted to a generally horizontal base portion 40B of a generally L-shaped mounting bracket 40. The remaining components of the system 10 are attached to the vertical leg 40L of the cart 40. The bracket 40 is itself attached to a frame 42 which supports axles 44A and wheels 44W. A handle 45 is attached to the vertical leg 40L.

[0035] As seen from FIG. 2B (and also in FIG. 3D) the physical interconnection of the air and liquid supplies to the foam generator 14 is made using a T-fitting 46. In the arrangement illustrated the air flow is introduced through the leg of the fitting 46 that aligns axially with the axis of the foam generating column 14C, while liquid is introduced through the leg of the fitting 46 perpendicular thereto.

[0036] The incorporation of the foam generating system 10 of the present invention into an apparatus for cleaning a carpet C may be understood from FIGS. 3A-3E.

[0037] Shown in FIGS. 3A through 3C is the basic structural elements of a carpet cleaning apparatus 50, such as that cleaning apparatus described in U.S. Pat. No. 6,367,109 (Besel and Lee), assigned to assignee of the present invention. The apparatus 50 includes a frame 52 that supports a rotary carpet cleaning assembly 54 and the drive motor therefor (not shown). A handle projects 52H upwardly and rearwardly from the back edge of the frame 52. The frame 52 also carries the axles 56A for wheels 56W.

[0038] The carpet cleaning assembly 54 includes a plate 54P that is rotationally mounted to the frame 52. A brush 54B is attached to the lower surface of the plate 54P, while a frustoconical baffle 54F is secured to the upper surface of the plate 54P. The volume on the interior of the baffle communicates with the brush 54B through foam supply passages 54S. In the environment of the carpet cleaning apparatus 50 the carpet cleaning assembly 54 serves as the user appliance for the foam generated by the foam generator 14.

[0039] A housing 58 is mounted to the frame 52. The interior of the housing 58 is hollow and defines a volume that serves as the supply tank 28. The housing 58 is closed by a vented cap 58C.

[0040] As is best seen in FIG. 3C lateral portions of the housing 58 extend rearwardly to define mounting wings 60A, 60B. The margin of each mounting wing 60A, 60B, as well as the rear margin of the housing 58, define mounting platforms 62A, 62B, 62C, respectively.

[0041] The components of the foam generating system 10 are mounted to a mounting plate 68 that takes the form of a “reverse 7”. The front and side edges of the top 68T of the plate 68 are received on the mounting platforms 62A, 62B, 62C and there secured by mounting bolts 70. The lateral edges of the leg 68L of the plate 68 are secured to the wings 60A, 60B, as by bolts 72.

[0042] The physical arrangement of the components of the foam generating system the surface of the leg 68L of the plate 68 is best seen in FIGS. 3D and 3E. The outlet line L from the foam generator 14 is connected to the carpet cleaning assembly 54 (the user appliance in this implementation of the invention) through a pipe P (FIGS. 3A, 3B) that is attached to the frame 52. Foam from the generator 14 enters to the volume on the interior of the baffle 54F through a nozzle N (FIGS. 3A, 3B).

[0043] However implemented, the foam generating system 10 of the present invention is seen to provide significant advantages over foam delivery systems of the prior art. Owing to the use of the positive displacement pump the liquid and foam delivery rates are independent of the pressure of the air supplied by the pressurized air source, the back pressure of the foam generator, the volume of liquid in the supply tank, and the pressure drop of the connection line. This is a significant advantage when the foam generator is used to feed portable application equipment that requires a steady flow for uniform deposition of foam over relatively long distances (on the order of one hundred feet).

[0044] Those skilled in the art, having the benefit of the teachings of the present invention, as hereinabove set forth, may effect numerous modifications thereto. It should be understood that all such modifications lie within the contemplation of the present invention as defined by the appended claims. 

What is claimed is:
 1. A foam generating system for delivering foam for use in a user appliance, the foam generating system comprising: a foam generator having an inlet port and an outlet port, the introduction of pressurized air and a liquid at the inlet port of the foam generator resulting in the delivery of foam at the outlet port thereof, during operation the foam generator having a predetermined back pressure associated therewith, the outlet port of the foam generator being connectable to a user appliance through a connection line having a predetermined pressure drop; a source for supplying pressurized air at a predetermined air pressure to the inlet port of the foam generator; and a supply tank for carrying a liquid; the improvement comprising: a vent through which the supply tank is vented to atmosphere; and a positive displacement pump operable at a constant liquid delivery rate for pumping liquid from the liquid supply tank to the inlet port of the foam generator, the liquid delivery rate from the pump to the inlet port of the foam generator being independent of the pressure of the air supplied by the pressurized air source, the back pressure of the foam generator, the volume of liquid in the supply tank, and the pressure drop of the connection line, whereby the delivery rate of foam from the outlet port of the foam generator for delivery to the user appliance (expressed as weight of foam per unit time) is substantially constant.
 2. A carpet cleaning apparatus comprising: a frame with a carpet cleaning assembly mounted thereon; and a foam generating system for delivering foam to the carpet cleaning assembly, the foam generating system comprising: a foam generator having an inlet port and an outlet port, the outlet port of the foam generator being connected to the carpet cleaning assembly through a connection line having a predetermined pressure drop; the introduction of pressurized air and a liquid cleaning agent at the inlet port of the foam generator resulting in the delivery of foam at the outlet port thereof, during operation the foam generator having a predetermined back pressure associated therewith, a source for supplying pressurized air at a predetermined air pressure to the inlet port of the foam generator; and a supply tank for carrying a liquid cleaning agent; the improvement comprising: a vent through which the supply tank is vented to atmosphere; and a positive displacement pump operable at a constant liquid delivery rate for pumping liquid cleaning agent from the supply tank to the inlet port of the foam generator, the liquid cleaning agent delivery rate from the pump being independent of the pressure of the air supplied by the pressurized air source, the back pressure of the foam generator, the volume of liquid cleaning agent in the supply tank, and the pressure drop of the connection line, whereby the delivery rate of foam from the outlet port of the foam generator for delivery to the carpet cleaning assembly (expressed as weight of foam per unit time) is substantially constant. 